Question: Who was the head coach of the Pittsburgh Steelers until December 26, 1991?
Paraphrase: Who stepped down as the head coach of the Pittsburgh Steelers on December 26, 1991?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q191477 p:P286 ?s . ?s ps:P286 ?obj . ?s pq:P582 ?x filter(contains(YEAR(?x),'1991')) }